Employee Benefit Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 28	$ 31	$ 57	$ 63
Interest cost	78	72	155	144
Expected return on plan assets	(139)	(133)	(278)	(266)
Amortization of prior service cost (credit)	1	1	1	1
Amortization of net actuarial loss	27	40	55	80
Net periodic benefit cost (credit)	(5)	11	(10)	22
Pension Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4	7	7
Interest cost	7	7	15	14
Expected return on plan assets	(34)	(32)	(67)	(63)
Amortization of net actuarial loss	4	5	7	10
Net periodic benefit cost (credit)	(19)	(16)	(38)	(32)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	10	16	20
Interest cost	17	16	34	33
Expected return on plan assets	(30)	(30)	(59)	(59)
Amortization of prior service cost (credit)	(7)	(6)	(14)	(13)
Amortization of net actuarial loss	2	2	3	3
Net periodic benefit cost (credit)	(10)	(8)	(20)	(16)
Other Postretirement Benefits | Dominion Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	3	3
Interest cost	4	4	7	7
Expected return on plan assets	(7)	(6)	(12)	(12)
Amortization of net actuarial loss	1	0	1	1
Net periodic benefit cost (credit)	$ 0	$ (1)	$ (1)	$ (1)